Bigger Lens or D800E

I shoot HS sports. Currently, I shoot with 300mm f2.8 on a D3s along the sideline, and behind the end zone if situation requires it. Yep, a lot of moving around players, coaches, ball boys, trainers, chain gang, etc. As the result, I miss some of the more desired action shots.

Another more experienced shooter shoot with a 400mm on a cropped camera, equivalent to a 600mm vs my 300mm lens, quite a big difference. So, he is able to stay in one area the entire game behind the goal line to get all shots. I can see the advantage of that location as he has a very clear view of split ends leaping for the ball, which I will miss because of sideline interference.

So, here is the debate. What do you think is best shooting night HS football if I want I to shoot from the end zone? For the best IQ after cropping, which do you think would give me the best results?